1. Field of the Invention
This invention relates to medical devices and, in particular, to delivery and deployment devices for self-expanding prostheses and methods of delivering and deploying a prosthesis into a body lumen.
2. Description of Related Art
Expandable prostheses, such as stents and stent grafts, are used for treating damaged or diseased body lumens such as the esophagus, bile duct, and blood vessels. The deployment of intraluminal prostheses into the lumen of a patient from a remote location by the use of a delivery and deployment device is well known in the art. Generally, an expandable intraluminal prosthesis is placed on a delivery and deployment device in a radially reduced state and inserted percutaneously into a body lumen. Once the prosthesis is properly positioned, the prosthesis may be radially expanded using means well known in the art. For example, the prosthesis may be expanded using a balloon catheter device.
Alternatively, the prosthesis may be radially self-expanding. Where the prosthesis is radially self-expanding, the delivery and deployment device will include means for retaining the prosthesis in a radially constrained state. For example, U.S. Pat. No. 4,562,596 entitled “Aortic Graft, Device and Method for Performing an Intraluminal Abdominal Aortic Aneurysm Repair,” which is herein incorporated by reference, proposes retaining a self-expanding graft within a sleeve until it is to be deployed, at which time the sleeve is withdrawn and the graft is allowed to expand. U.S. Pat. No. 4,665,918 entitled “Prosthesis System and Method,” which is herein incorporated by reference, proposes a system and method for the deployment of a prosthesis in a blood vessel. The prosthesis is positioned between a delivery catheter and an outer sheath, and expands outwardly upon removal of the sheath.
A problem with conventional delivery and deployment systems for radially self-expanding prostheses is that the accuracy and precision of prosthesis placement is dependent on the axial stiffness of the prosthesis. During deployment, the delivery and deployment device imposes stresses on the prosthesis, for example, via friction between the retaining sleeve and the prosthesis. Axially stiff prostheses are generally capable of absorbing these stresses without exhibiting significant axial shortening or elongation. Axially flexible stents, however, are more sensitive to axial stresses and may be more prone to exhibit axial shortening or elongation during deployment, resulting in potentially inaccurate or imprecise prosthesis placement in the body lumen. There is a growing need for axially flexible prostheses that are capable of conforming with highly deformable luminal environments, such as the superficial femoral artery. Accordingly, there is a need in the art for a prosthesis deployment system that reduces or eliminates the problem of axial shortening or elongation.
U.S. Pat. No. 5,201,757 entitled “Medial Region Deployment of Radially Self-Expanding Stents,” which is herein incorporated by reference, proposes an apparatus for deploying a radially self-expanding stent. The apparatus includes proximal and distal sleeves for containing proximal and distal end portions of the stent in a reduced radius delivery configuration. The sleeves are moved axially relative to one another to permit radial self-expansion of the stent. A problem with this system is that it does not provide the operator with sufficient control over the manner of deployment. For example, if the operator wishes to deploy the prosthesis in a single quick motion, he will be unable to control the rate or the order of deployment of the proximal and distal prosthesis ends. This is because the manner of deployment can be significantly impacted by internal frictional stresses that can vary from device to device. The operator may also wish to deploy the distal sleeve prior to the proximal sleeve, or the proximal sleeve prior to the distal sleeve. Alternatively, the operator may wish to deploy the proximal and distal sleeves concurrently. The system disclosed in U.S. Pat. No. 5,201,757, however, is generally not capable of providing this level of control to the operator. As a consequence, there is a need in the art for a prosthesis deployment system that solves these and other problems.